Which macronutrient is most mobile within crop plants?

Nitrogen is considered the most mobile macronutrient within crop plants. This mobility can be attributed to its chemical form and how plants uptake and utilize the nutrient. Nitrogen is readily absorbed in the form of nitrate (NO3-), which is highly mobile in the soil and can easily move with the soil water. This mobility allows nitrogen to be translocated within plant tissue efficiently, enabling it to be moved to various parts of the plant as needed, particularly during growth stages when demand is high.

In contrast, phosphorus and potassium have different mobility characteristics. Phosphorus tends to form complexes in the soil that limit its mobility, making it less available in comparison to nitrogen. Potassium is more mobile than phosphorus but not to the extent of nitrogen, as it can be taken up in both soluble and fixed forms, although it does not move through plant tissues as swiftly. This distinction highlights nitrogen's unique role in plant nutrition and growth, particularly during critical development phases.